Strapped to walls in public places around the United States are simple battery-powered devices that already have saved thousands of people and could save many more if the pool of trained users were greater.

The number of the heart-starting defibrillators deployed across the nation and how they are used was underscored in a recent incident at an Orange County health club.

Bill Sanches, a 57-year-old electrician, collapsed soon after he strolled into a 24 Hour Fitness center in Irvine. His heart had stopped as suddenly as if an ignition switch had been turned off, which is close to what happened. His body’s electrical system failed.

Fortunately for Sanches, at least two physicians and a registered nurse were close by, working out. Dr. David Abrahamson reached Sanches first and began cardio-pulmonary resuscitation; Dr. John Bailey delivered breaths. About a minute later, Jennifer Woolley arrived, carrying the defibrillator that was installed at the health club. The registered nurse had been trained on the device and knew how to use it.

Within about a minute of Woolley’s arrival, the defibrillator was in place and discharged. Seconds later, Dr. Abrahamson felt a pulse. About five minutes had elapsed since Sanches had dropped to the floor.

Sanches not only survived, he had been attended to so quickly that his heart remained undamaged, Abrahamson said.

But what if no doctors or nurse had been present?

24 Hour Fitness declined to discuss the incident except to say that it had “procedures and staff training in place” and that four staffers on duty were certified in CPR and the use of the defibrillator.

But time is life when someone’s heart stops. Doctors say a heart failure victim has a 70 percent chance of survival if cardio-pulmonary resuscitation (CPR) and a defibrillator can be applied within 2-3 minutes. After that, the victim’s chances of survival decline by 10 percent each minute.

About 685 people a day in the United States die of heart failure, according to the American Heart Association. No one keeps statistics on how many people die within reach of a defibrillator or because people could not figure out how to use them in time, but an association study found about a quarter of cardiac arrest victims lived when they received prompt CPR and a heart-starting shock from a defibrillator.

A 2004 report in the Journal of Family Practice questioned the effectiveness of the widespread installation of defibrillators, and the fire captain who arrived with paramedics after Sanches fell in the fitness center said it was the first time he had even seen a defibrillator in a public place properly used.

Still, there have been some defibrillator successes. Mike Gorman, a defibrillator expert with Phillips, the electronics giant, says that 70 passengers in recent years on American Airlines jetliners have been saved by defibrillators.

If only more people knew how to use them.

From July 2005 to June 2006, 23,440 people were trained in the use of defibrillators through 500 authorized training providers, according to figures from the Orange County chapter of the American Red Cross.

That’s less than 1 percent of the county population, and although voice prompts typically tell how to use the device, it can take time for an untrained user to determine how to deal with a patient with jewelry, a pacemaker or a very hairy chest.

New-generation defibrillators are easy to use, doctors and the companies that make them say, and certification classes take just a few hours.

Zee Medical in Huntington Beach trains staffers at 24 Hour Fitness and other companies in CPR and the use of defibrillators. Zee recommends 10 percent of the staff where a defibrillator is installed be trained in using the device and in CPR, says Linda Hunter, a certified trainer with the company.

Contact the writer: Orange County Register researcher Colleen Robledo contributed to this report.